Wireless control networks have recently become a ubiquitous trend in the field of communication, especially for building management systems. Wireless technologies present major advantages in terms of freedom of placement, portability, and installation cost reduction, since there is no need for drawing cables and drilling. Thus, such technologies are particularly attractive for interconnecting, detecting, automation, control or monitoring systems using sensor devices such as light switches, light dimmers, wireless remote controllers, movement or light detectors, that have to be set up in distant places one from the other and from the devices they control, e.g. lights.
One of the drawbacks appearing in networks of the like relates to device powering. Indeed, since the devices are not wired, they can not anymore receive power necessary for performing all the operations required in the network form the mains or via the connection with the controller. Thus, it has been envisaged to equip such devices with built-in batteries. However, since the devices are quite size-constrained, batteries may not be of a large size, which results either in a reduced device lifetime, or in labour intensive battery replacement.
It has been suggested to remedy this issue by equipping sensor devices with self-sustained energy sources that harvest energy from its environment. Still, the amount of energy achievable by off-the-shelf energy harvesters is very limited, which means that the features and functions of the batteryless devices are heavily restricted accordingly.
Among the functions that are mandatory to be maintained for good operation in a wireless network is the link connection, which makes it possible to ensure at any time that a resource restricted device is linked to a router which forwards messages on its behalf. In existing implementations therefore, a parent-child relationship is established between an end device, generally resource-restricted, and its parent. The child end device addresses all its communication to the parent for being forwarded to their final destination. However, in case of energy-harvesting device, this relationship creates a single point of failure in the network, because in case the parent link is broken, communication from the end device can not be successfully performed anymore. Moreover, in most cases, such a failure may not even be detected by the end device, due to non-existent or not used return path, or insufficient energy.
Thus, there is a need for a method of communicating ensuring maintenance of good operation in a wireless control network. Moreover, as explained before, there is a need for a method that can be carried out without using too many resources of the end device, since those devices are generally resource-constrained, namely in terms of energy resources.